Various vehicular tires have been proposed which are composed of, or contain a component composed of, polyurethane. The polyurethane is typically the reaction product of an organic polyisocyanate and polymeric polyol, or reaction product of polyamine and isocyanate terminated pre-polymer of polyisocyanate and polymeric polyol.
The polyurethane is a cast polyurethane in a sense of being the product of casting a liquid polyurethane reaction mixture into a suitable mold cavity and allowing the liquid reaction mixture to react within the mold and form the molded polyurethane product without being sulfur or peroxide cured. The cast polyurethane for this invention does not contain an unsaturated hydrocarbon component and is there not susceptible to sulfur vulcanization.
The cast polyurethane for this invention is intended to be distinguished from and exclusive of a millable polyurethane composed of a product of a polyurethane reaction mixture containing unsaturated hydrocarbon component(s) which is sulfur or peroxide cured.
When the cast polyurethane is a reaction product of polyamine and isocyanate terminated pre-polymer which might more appropriately be referred to as a polyureaurethane, it is referred herein in more general terms as being a polyurethane.
Exemplary of such tires composed of or containing polyurethanes are, for example, and not intended to be limitive, U.S. Pat. No. 4,095,637 relating to a solid polyurethane tire/wheel assembly and U.S. Pat. Nos. 4,295,513, 4,131,667 and 8,662,122 in general.
In practice, tires are generally subject to dynamic flexing during their service and operation. For tires which are composed of or which contain a component comprised of polyurethane, it is sometimes desired to provide reinforcement for polyurethane. Here, it is desired to evaluate use of particulate boron nitride in a form of a composite of hexagonal boron nitride platelets, or h-BN, for providing reinforcement for the polyurethane.
Historically, tires have been proposed having vulcanizable rubber components containing a dispersion of boron nitride to promote improved heat transfer and having an innerliner with resistance to air permeability containing a dispersion of boron nitride. Such vulcanizable rubber components are composed of rubbery polymers or elastomers that are capable of being crosslinked or vulcanized. Such polymers are said to include, but not limited to synthetic polymers such as synthetic polyisoprene, polybutadiene, polysulfide rubber acrylic rubber, urethane rubber and silicone rubber. For example, see U.S. Pat. No. 8,735,487.
Boron nitride is a chemical compound with a chemical formula represented as BN which consists of equal numbers of boron and nitrogen atoms which exists in various crystalline forms. The hexagonal form (which may sometimes be referred to herein as h-BN) is a layered boron nitride configuration which is composed of hexagonal crystalline stacked layers and is considered to be a stable form which exhibits good thermal and chemical stability. It is sometimes used as an additive in various lubricant and cosmetic products. It has been used in rubber compositions for various purposes. As indicated, it is desired to evaluate the h-BN for use as a particulate reinforcement for polyurethane.
It is envisioned that hydrogen bond linkages can be created between the h-BN and isocyanate of the polyurethane reaction mixture which can thereby promote reinforcement of the polyurethane for improvement of one or more of its physical properties.
Optionally, a desiccant such as dry molecular sieves may be blended with one or more of the h-BN, polymeric polyol and polyamine to promote removal of moisture or to prevent moisture interference with the polyurethane reaction mixture.
Therefore, in one embodiment of the invention, a desiccant in a form of dried molecular sieves may be mixed with, or together with, at least one of the h-BN, polymeric polyol and polyamine and then mixed with a polyisocyanate to create a moisture free polyurethane reaction mixture. In such case, the ultimate polyurethane product will contain the molecular sieves.